use_reduce: Give a hint to IUSE in the 'use flag '%s' is not referencable in conditio...

diff --git a/pym/portage/dep/__init__.py b/pym/portage/dep/__init__.py
index 5ec04cfc3d98dad5ec4a5a10baf1cfe1b8cecdd8..8fc472819c7ab04cf8c950385a04475feb8a0bac 100644 (file)
--- a/pym/portage/dep/__init__.py
+++ b/pym/portage/dep/__init__.py
@@ -306,7 +306,8 @@ def use_reduce(depstr, uselist=[], masklist=[], matchall=False, excludeall=[], i
                if is_valid_flag:
                        if not is_valid_flag(flag):
                                raise portage.exception.InvalidDependString(
-                                       _("use flag '%s' is not referencable in conditional '%s' in '%s'") % (flag, conditional, depstr))
+                                       _("use flag '%s' is not referencable in conditional '%s' in '%s' (flag missing from IUSE?)") \
+                                               % (flag, conditional, depstr))
                else:
                        if _valid_use_re.match(flag) is None:
                                raise portage.exception.InvalidDependString(